PHP 7.4 brings a lot of exciting new features. One of them is the Foreign Function Interface extension built directly into the core. But what problems exactly this extension is trying to solve? Does this mean that we no longer need to write a PHP extension if we want to use an existing library? In this article, we will discover how to call almost any C library directly from PHP easily, how to overcome common pitfalls, when to use this approach, and most importantly, when not.